Laboratory Investigations in Support of Carbon Dioxide-in-Water Emulsions Stabilized by Fine Particles for Ocean and Geologic Sequestration of Carbon Dioxide

This semi-annual progress report includes our latest research on deep ocean sequestration of CO{sub 2}-in-Water (C/W) emulsions stabilized by pulverized limestone (CaCO{sub 3}). We describe a practical system that could be employed for the release of a dense C/W emulsion. The heart of the system is a Kenics-type static mixer. The testing and evaluation of a static mixer in the NETL High-Pressure Water Tunnel Facility was described in the previous semi-annual report. The release system could be deployed from a floating platform over the open ocean, or at the end of an off-shore pipe laying on the continental slope. Because the emulsion is much denser than ambient seawater, modeling shows that upon release the plume will sink much deeper from the injection point, increasing the sequestration time for CO{sub 2}. When released in the open ocean, a plume containing the output of a 500 MW{sub el} coal-fired power plant will typically sink hundreds of meters below the injection point. When released from a pipe on the continental shelf, the plume will sink about twice as much because of the limited entrainment of ambient seawater when the plume flows along the sloping seabed. Furthermore, the plume is slightly alkaline, not acidic. The disadvantage is that the creation of the emulsion requires significant amounts of pulverized limestone, on the order of 0.5-0.75 weight ratio of limestone to CO{sub 2}. While pulverized limestone with particle size appropriate for creating C/W emulsions can be purchased for $38 per ton, it is shown in this report that it may be more economic to purchase raw limestone from quarries and pulverize it in situ using grinding mills. In this case the major cost elements are the capital and operating costs of the grinding mills, resulting in a total cost of about $11 per ton of pulverized limestone, including the cost of raw material and shipping. Because we need approximately 0.75 ton of pulverized limestone per ton of liquid CO2 to create a stable C/W emulsion, the total cost of preparing the emulsion on site is about $8.5 per ton of liquid CO{sub 2}, not including the cost of the emulsion mixer. Currently, the cost estimates of capturing and liquefying CO{sub 2} at a coal-fired power plant range from $15 to 75/t CO{sub 2}. Thus, the preparation of C/W emulsions stabilized by pulverized limestone particles would add about 10 to 50% to the capture cost of CO{sub 2}. At this juncture the primary research objectives of this Co-operative Agreement are shifting toward geologic sequestration of carbon dioxide. Experiments are underway to create micro-emulsions of CO{sub 2}-in-Water (C/W) and Water-in-CO{sub 2} (W/C) stabilized by ultrafine particles ranging from sub-micrometer to a few micrometer in size. Such microemulsions are expected to readily penetrate deep geologic formations, such as porous sedimentary layers, including saline aquifers and semi-depleted oil and gas fields. Injections of (C/W) and (W/C) type micro-emulsions may prove to be less prone to leakage from the formations compared to injections of neat liquid or supercritical CO{sub 2}